Digestion and Absorbtion

- Digestive enzymes are used to break down biological molecules in the food.

- Enzymes are specific and can only break down substrates that have a complementary shape with their active site.

-Amylase is an enzyme that is used to convert starch into a smaller sugar maltose, using hydrolysis reaction.

- Amylase is produced by the salivary gland ( released inside the mouth ),also by pancreas which releases the enzymes in small intestine.

Glucose + Glucose = Maltose

Glucose + Fructose = Sucrose

Glucose + Galactose = Lactose  

- Lipase break down lipids into monoglycerides and fatty acids. This involves the hydrolysis of the ester bonds. Lipase are made in pancreas and work in the small intestine.

- Bile salts are produced by the liver and cause the lipids to form small droplets (emulsify).

- Several small lipid droplets have a greater surface area than a single large l droplet.

- The greater the surface area, the easier it is for Lipase ( enzymes ) to ge to droplets and break them down.

Proteins are broken down by different combination of proteases. They catalyse the conversion of proteins into amino acids via hydrolasation.

Endopeptidases

- Act to hydrolysis the bonds within a protein

- Trypsin and Chymotrypsin are two examples of this that are produces in pancreas and released into the small intestine.

Exopeptidases:

- Act to hydrolyse to remove a single amino acid from the end of the protein.

- Dipeptideases is an example of it that works specifically on dipeptides. They are often located in the cell surface membrane of epithelial cells of small intestine.

The products of the Digestion are absorbed through the ileum epithelium ( in the small intestine ) into the bloodstream.

--> Monosaccharides

      * Glucose ( as well as Galactose ) is absorbed by active transport of         sodium ions via cotransporter protein. 

      * Fructose is absorbed via facilitated diffusion.

--> Monoglycerdes and fatty acids

      * Micelles help to move them towards the epithelium

--> Amino acids

      *They absorbed the same way as the glucose via sodium ions.